Method of mounting coiled-coil filmaents



Feb. 7, 1939.

w. E. ANDERSON ET AL METHOD OF MOUNTING COILED-COIL FILAMENTS Filed Jan. 51, 1956 h. E. A/VDfRSO/V 6- 14.

Patented Feb. 7, 1939 auaan n mrno or uomrmm comm-con.

' mam-rs E. Iontclair, andGeoI-ge A.

- 1 Freeman, MN. J., a-ignors, by mesne aaignmenh, to Wm Manufacturing Company. East --a corporation of Pennsylvania use Electric and Pittsburgh, Pa...

Application January :1. 193's. Serial No. 61,688

11 China.

This invention relates to the manufacture'of incandescent electriclamps and relates more particulariy to the use of i concentrated or coiled-coil filament.

- Developments in the production [of incandes- "cent electric lamps has brought about a filament construction wherein the usual helically coiled filament is again coiled to produce a coiled-coil.

' Coilsof this character aremade" either by windingv ahelicaily coiled filament on a mandrel and then removing themandrel, or by coiling the helically coiled filament into a secondary coil in mounting the coils. When a coiledcoil is made it is necessary to heat-treat the coil to set the turns.

When, for example, a coiled-coil is made j by windinga wire on a mandrel, the coil is given .aheat treatment at as high, a temperature as the mandrel will stand. It has been found, however, that even when treating at a higher temperature,

. as when no mandrel is used, the turns of the secondary coil will contract or draw in during the subsequent lighting up and burning of the filament in a lamp." In other words, the secondary I coil will have a greater number of tums'per inch that when originally wound and the necessary control of the turns per inch is lost.

This condition does not appear during the process of coil manufacture since the heat treatment sets the coils while on the mandrel. When a mandrel is used, and even afterthe mandrel is A removed the coils still remain fixed as to turns per inch. The internal stresses are not sumcient to change the spacing of the turns.

When the filament is subjected to the operat ing temperature during use in a lamp, either the internal stresses are released with attending physical movement of the turns, or new. forces are brought about producing the same result. If a coiled-coil filament is mounted in a lamp in the ordinary manner andthe lamp Put into opera- I I tion; forces are released andthe turns of the coil move closer together. Furthermore, this'move- [ment or contraction is irregular, causing localized heating with a consequent reduction inthe usefulilife of the lamp. d

"A lamp filament is constructed in accordance with definite rating specifications which obviwhat is known as a coiled-' ously include the length and diameter of wire and coil and particularly the spacing of the turns. Any change in the spacing of a coiled-coil, as

' when" the spacing of the turns of the secondary winding is reduced; results in short life for lamps rated to operate at a given voltage. In lamps where the initial lumens. per watt varied over a wide range, it was found that the useful lives of the lamps didnot vary with the initial efliciency in the same relation as is the case when the single helically coiled filament is used.

It is an object of the present invention to provide a mounted coiled-coil filament which may be operated in a lamp without change in the filament structure detrimental to the efficient and useful life of the lamp.

Another object of the invention isto provide a method or mounting acoiled-coil filament so as to restrict the relative movement of tums to maintain a predetermined space relation therebetween.

A further object of the invention is to provide a method of mounting a coiled-coil filament so as to prevent a decrease in the space relation of the turns of the filament under operating conditions.

I A still further object of the invention is to provide a lamp mount so constructed as to controlthe turns per inch. of the filament under operating conditions. v Other objects and advantages of the invention 'will be more clearly understood by reference to the following description together with the accompanying drawing in which:

Fig. 1 is a side elevational view of a lamp having a coiled-coil filament mounted in accordance with the present invention;

Fig. 2 is an enlarged view taken on line 11-11 in Fig. 1;

Fig. 3 is a side view of the mounted filament ,shown in Fig. 2;

Fig. 4 shows a complete stem or mount constructed as shown in Fig. 1, but before being sealed to a bulb;

Fig. 5 is a modified form of the coiled-coil mounting;

Fig. 6 is a side view of the modified form of mounting shown in Fig. 5; and

'Fig. 7 is a view taken on line VII-VII in Fig. 6.

The present inventionis shown as applied to an incandescent electric lamp comprising a bulb II in which a. mount II is sealed and exhausted in the usual manner after which a base I! is provided to complete the lamp.

As shown in Fig. 4,- a mount includes a flare tube l3 having a press l4 from which extends an arbor l5 having an enlargement or bead I 5'.

' The flare tube is provided with the usual .ex-

haust tube I 0, and lead wires l1 and I8 extend upwardly from the press.

The terminals I 9 and of a coiled-coil fila- I are of sumcient thickness and rigidity to serve as supports for the filament.

In accordance .with the selected embodiment of the present invention a coiled-coil is mounted by first connecting the terminals 19 and 20 of the coil to the upper ends of the supports 22 and 23 by' welding or clamping. The coil is then.

stretched to a predetermined length by separating the support members; as shown in Fig. 3. The support members are then secured in their separated relation by brace members 24 and 25 which may consist of malleable wires having their ends embeddedin the bead II. The free ends of the brace members 24 and 25v are then tightly wound aroundthe support wires 22 and 23, respectively. or are looped thereabout to form eyelets 26 and 21 which enclose the support wires and keep them from'moving toward each other when the coil tends to contract, and obviously v preventing the coil from shortening.

,If the brace members are tightly wrapped about or, if desirable, welded to the support wires, it may be desirable to first secure the brace members to the support wires and then connect the ends of the'fllament to the ends of the support wires. The filament may then be stretched by bending the support wires in opposite directions about their points of'attachment to the brace members.

In addition to the support wires, an intermediate support or guide member 28 may be provided. This member, as shown, is in the form of a wire extending upwardly from the bead l5 and is provided with a loop which encircles the filament and serves to limit the movement of the filament in the case of vibration, or if it droops during the operation of the lamp. The filament should, however, float freely in the loop of this support which merely acts as a means for arresting excessive movement. In Fig. 5, however, the center support 34 also serves to produce the required tension in the filament.

When producing a mount by the present method, the degree of stretching will vary depending on the wattage of the lamp in which the coil is to be used. For example, in a lamp of sixty watts a coiled-coil of forty-three turns is used, having a length of twenty millimeters between the support wires, and is stretched to about twenty one millimeters. I 1

Figs. 5 to 7 show a modification of the present method of mounting in which a coil 30, having sections 3| and 32 separated by a straight portion 33, is mounted on a stem. The support members 22 and 23 may be the same as in Fig. 4,. but a central support 34 extending at an angle to the vertical axis of the arbor is provided. This central support has a loop which encircles the straight portion 33 and when the coil is mounted the support wires may be separated to stretch the coil and then welded at 35' and 36, or a loop as shown in Fig. 4 may be used. The central support 34 may be bent outwardly to take up slack and aid in stretching the coil.

As above pointed out, in making an incandescent electric lamp it is important to hold the filament to a predetermined number of turns per inch. This means that the spacing between must be held constant. When using the single helically coiled filament, the filament when heated during operation tended to stretch since the heat caused the metal to expand.

7 When using the.coiled-coil filament, heat during operation expands the metal, but owing to the free play or movement of .the secondary coil the turns increase slightly in diameter with the result that the distance between the turns decreases. The secondary coil is very flexible and responsive to slight forces, and, in accordance with the present invention, advantage is taken. of this characteristic and when the filament is mounted it-is held against contraction until'the high temperature to which the. filament is subjected releases any potential or internal force which would tend to causethe turns to change their space relation.

After these forces have been released, thecrystal structure of the filamentary wire takes a set and the turns remain in definite space relation.

Although the present method provides for the stretching of the coil in order to insure a definite space relation of the turns, it will be understood that it is in fact only necessary to secure the terminals of the filament to restrict the movement of the turns when subjected to operating temperature. In actual practice it would be difiicult to secure the ends of the filament wires spaced the exact distance apart so the coil is designed in such a way that the required turns per inch are attained by stretching the coil to give the required number of turns per unit of length, and, as above pointed out, this length is maintained during the operation of the lamp.

stretched length, it is immaterial whether or notthe stretching operation is performed before the filament is secured to the supports or held with the turns in a given spaced relation, and mounted so that no contraction can occur after the filament is heated during operation in a lamp.

The foregoing description gives a practical use of the present invention and sets forth the method of producing .a mount or lamp in which the advantagesof the invention are attained.

It has been found that by reason of the above described method of mounting a coiled-coil a lamp is produced in which the uniformity of rating and the life is greatly improved ata given efficiency without the sacrifice of strength.

Although a preferred embodiment of the inven tion is shown and described herein, it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

We claim:

1. The method of mounting a coiled-coil filament for an incandescent electric lamp on support members of a lamp stem which comprises stretching to provide a desired space relation between the secondary turns and securing the terminals to support members, so as to restrict the movement of the turns of thecoil to maintain said space relation between the turns during the operation of the lamp.

2. The method of mounting a coiled-coil filament which comprises winding said filament with a predetermined space relation between the turns It will be understood, therefore, that the inven- 0! the secondary coil thereof, increasing the space relation between said secondary turns to provide a secondary coil having a given number of secondary turns per unit of length and restricting the movement of said turns to maintain said given space relation when the coil is heated durlng operation in a lamp. i

3. The method of maintaining a predetermined space relation between the secondary turns of the secondary coil of a coiled-coil filament during operationwhich .comprises stretching the said coil to provide a space relation between the secondary turns greater than the space relation ai'ter winding and securing the terminals 01' the stretched filament to the ends of support wires of suflicient rigidity to hold the filament during 'operation against contraction detrimental to the useful life of the lamp. Q

d. The method of mounting a coiled-coil filament which comprises securing the terminals of a filament to ends of the support members of a lamp stem, separating the support members to applytension to the filament, and securing the separated support members in fixed relation to prevent a contraction of the secondary coils of the filament when heated during operation.

5. The method of mounting a coiled-coil fila- .ment on a stem having a pair of support'wires and an arbor disposed between said wires which comprlses'securing' the terminals of a filament to endsof saidsupport wires, moving to separate the support wires to hold the filament taut, and

'securing the support wires to said arbor in fixed relation in their separated positions to prevent the secondary coils of said filament from contractlng when heated during operation.

6. The method of mounting a coiled-coil filament on a stem having apair of support wires, an arbor and members extending laterally from said arbor which comprises securing the termiso spaced that said filament is under such tension when cold that the secondary coil spacing is maintained when heated.

8. A mount for an incandescent electric lamp comprising a 'reentrant tube having a press, an arbor extending therefrom, a pair of support wires extending throughsaid press and disposed on opposite sides of said arbor, a stretched coiledcoil filament, the ends of which are secured to the'ends of said support wires, providing the desired turn spacing between said support wires, and bracing members the inner ends of which are secured to said arbor and the outer ends of which engage said support wires to hold them in separated position and prevent undesired contraction of the filament when heated during operation.

9. A mount for an incandescent electric lamp comprising a reentrant tube having a press, an arbor extending therefrom, a pair of support wires extending through said press and disposed on opposite sides of said arbor, a stretched coiledcoil filament, the ends or which are secured to the ends of said support wires, providing the desired turn spacing between said support wires, and preventing undesired contraction of the fila= ment when heated during operation.

10. An incandescent electric lamp having a bulb, a stem sealed to said bulb, a pair of support wires extending from said stem, an arbor disposed between said wires, a stretched coiled- .coil filament having a wound length providing a turn spacing corresponding with that desired in operation, the ends of said coil being secured to the ends of said support wires, and braces with their ends respectively secured to said arbor and engaging intermediate portions of said support wires, for holding said filament in its streched condition, and preventing undesired contraction thereof when heated during operation of the lamp.

11. An incandescent electric lamp having a bulb, a stem sealed to said hub, a pair of support wires extending from said stem, an arbor disposed between said wires, a stretched coiledcoil filament having a wound length providing a turn spacing corresponding with that desired in operation, the ends of said coil being secured to the ends of said support wires, for holding said filament in its stretched condition, and preventing undesired contraction thereof when heated during operation 01' the lamp.

WALDEMAR E. ANDERSON. GEORGEA. FREEMAN. 

